Oligocene TEX&amp;lt;sub&amp;gt;86&amp;lt;/sub&amp;gt;-derived seawater temperatures from offshore Wilkes Land (East Antarctica)

Hartman, Julian D.; Sangiorgi, Francesca; Salabarnada, Ariadna; Peterse, Francien; Houben, Alexander J. P.; Schouten, Stefan; Escutia, Carlota; Bijl, Peter K.

doi:10.5194/cp-2017-153

Cited by 2 publications

(8 citation statements)

References 85 publications

(155 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First of all, our observations suggest that Oligocene glacial-interglacial cycles were connected to substantial paleoceanographic dynamics off Wilkes Land. In agreement with the 2-3 • C SST variability as documented for this site during glacial-interglacial cycles (Hartman et al, 2017), dinocyst assemblages contain more oligotrophic, temperate dinocysts during interglacial times compared to glacial times when more eutrophic, colder dinocysts proliferated (Fig. 7).…”

Section: Surface Paleoceanographysupporting

confidence: 88%

“…Salabarnada et al (2018) interpret bottom-current activity in the Oligocene at Site U1356 and suggest it may be spilling over from the Ross Sea, like today. Our dinocyst results and the SST reconstructions by Hartman et al (2017) suggest that surface waters at the Wilkes Land margin were too warm to allow local bottom-water formation; therefore our data also support the suggestion that bottom water along the Wilkes Land margin was sourced from the Ross Sea.…”

Section: Implications For Oligocene-miocene Ocean Circulationsupporting

confidence: 82%

“…These assemblages prevail in surface waters with mean annual temperatures of 8-17 • C (Prebble et al, 2013) and therefore suggest relatively warm surface water temperatures close to the Wilkes Land margin. In support of this, a Bayesian approach on the TEX 86 index values at Site U1356 (presented in Sangiorgi et al, 2018;Hartman et al, 2017) also suggests the Southern Ocean mid-latitudes as a modern-analogue region and reconstructs a paleotemperature range of 8-20 • C for the Oligocene-Miocene at Site U1356, with values in excess of 24 • C for the late Oligocene (Hartman et al, 2017). Further, supporting evidence for temperate Oligocene-Miocene surface waters comes from the abundance of nannofossils encountered in the sediments (Escutia et al, 2011;Salabarnada et al, 2018).…”

Section: Sea-surface Temperaturementioning

confidence: 85%

“…Given the offshore geographic setting, we therefore infer that surface waters at Site U1356 experienced upwelling associated with the AAPF during most of the Oligocene and Miocene. We can exclude the possibility that nutrients were brought to the site via river run-off given the anticipated small catchment area that experienced liquid precipitation in the Wilkes Land hinterland, the low amounts of terrestrially derived (amorphous) organic matter in the palynological residues and relatively low branched over isoprenoid tetraether (BIT) index values (Hartman et al, 2017) that indicate predominantly marine organic matter. The exception may be the MMCO when considerable soil-derived organic matter reached the site.…”

Section: Surface-ocean Nutrient Conditionsmentioning

confidence: 99%

“…We further compare the palynological data with lithological observations and their interpretations from Salabarnada et al (2018). Pairing the sedimentological interpretations and biomarker-derived absolute sea-surface tem- perature (SST) reconstructions from Site U1356 (Hartman et al, 2017) with our dinocyst assemblage data, we reconstruct the paleoceanographic conditions off Wilkes Land and assess their variability on both glacial-interglacial and longer-term timescales.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 2: Insights from Oligocene–Miocene dinoflagellate cyst assemblages

et al. 2018

Self Cite

View full text Add to dashboard Cite

Abstract. Next to atmospheric CO 2 concentrations, iceproximal oceanographic conditions are a critical factor for the stability of Antarctic marine-terminating ice sheets. The Oligocene and Miocene epochs (∼ 34-5 Myr ago) were time intervals with atmospheric CO 2 concentrations between those of present-day and those expected for the near future. As such, these past analogues may provide insights into ice-sheet volume stability under warmer-than-presentday climates. We present organic-walled dinoflagellate cyst (dinocyst) assemblages from chronostratigraphically wellconstrained Oligocene to mid-Miocene sediments from Integrated Ocean Drilling Program (IODP) Site U1356. Situated offshore the Wilkes Land continental margin, East Antarctica, the sediments from Site U1356 have archived the dynamics of an ice sheet that is today mostly grounded below sea level. We interpret dinocyst assemblages in terms of paleoceanographic change on different timescales, i.e. with regard to both glacial-interglacial and long-term variability. Our record shows that a sea-ice-related dinocyst species, Selenopemphix antarctica, occurs only for the first 1.5 Myr of the early Oligocene, following the onset of full continental glaciation on Antarctica, and after the Mid-Miocene Climatic Optimum. Dinocysts suggest a weaker-than-modern sea-ice season for the remainder of the Oligocene and Miocene.The assemblages generally bear strong similarity to presentday open-ocean, high-nutrient settings north of the sea-ice edge, with episodic dominance of temperate species similar to those found in the present-day subtropical front. Oligotrophic and temperate surface waters prevailed over the site notably during interglacial times, suggesting that the positions of the (subpolar) oceanic frontal systems have varied in concordance with Oligocene-Miocene glacial-interglacial climate variability.

show abstract

Section: Surface Paleoceanographysupporting

confidence: 88%

Section: Implications For Oligocene-miocene Ocean Circulationsupporting

confidence: 82%

Section: Sea-surface Temperaturementioning

confidence: 85%

Section: Surface-ocean Nutrient Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 2: Insights from Oligocene–Miocene dinoflagellate cyst assemblages

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 1: Insights from late Oligocene astronomically paced contourite sedimentation

et al. 2018

Self Cite

View full text Add to dashboard Cite

Abstract. Antarctic ice sheet and Southern Ocean paleoceanographic configurations during the late Oligocene are not well resolved. They are however important to understand the influence of high-latitude Southern Hemisphere feedbacks on global climate under CO2 scenarios (between 400 and 750 ppm) projected by the IPCC for this century, assuming unabated CO2 emissions. Sediments recovered by the Integrated Ocean Drilling Program (IODP) at Site U1356, offshore of the Wilkes Land margin in East Antarctica, provide an opportunity to study ice sheet and paleoceanographic configurations during the late Oligocene (26–25 Ma). Our study, based on a combination of sediment facies analysis, magnetic susceptibility, density, and X-ray fluorescence geochemical data, shows that glacial and interglacial sediments are continuously reworked by bottom currents, with maximum velocities occurring during the interglacial periods. Glacial sediments record poorly ventilated, low-oxygenation bottom water conditions, interpreted as resulting from a northward shift of westerly winds and surface oceanic fronts. Interglacial sediments record more oxygenated and ventilated bottom water conditions and strong current velocities, which suggests enhanced mixing of the water masses as a result of a southward shift of the polar front. Intervals with preserved carbonated nannofossils within some of the interglacial facies are interpreted as forming under warmer paleoclimatic conditions when less corrosive warmer northern component water (e.g., North Atlantic sourced deep water) had a greater influence on the site. Spectral analysis on the late Oligocene sediment interval shows that the glacial–interglacial cyclicity and related displacements of the Southern Ocean frontal systems between 26 and 25 Ma were forced mainly by obliquity. The paucity of iceberg-rafted debris (IRD) throughout the studied interval contrasts with earlier Oligocene and post-Miocene Climate Optimum sections from Site U1356 and with late Oligocene strata from the Ross Sea, which contain IRD and evidence for coastal glaciers and sea ice. These observations, supported by elevated sea surface paleotemperatures, the absence of sea ice, and reconstructions of fossil pollen between 26 and 25 Ma at Site U1356, suggest that open-ocean water conditions prevailed. Combined, this evidence suggests that glaciers or ice caps likely occupied the topographic highs and lowlands of the now marine Wilkes Subglacial Basin (WSB). Unlike today, the continental shelf was not overdeepened and thus ice sheets in the WSB were likely land-based, and marine-based ice sheet expansion was likely limited to coastal regions.

show abstract

Oligocene TEX<sub>86</sub>-derived seawater temperatures from offshore Wilkes Land (East Antarctica)

Cited by 2 publications

References 85 publications

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 2: Insights from Oligocene–Miocene dinoflagellate cyst assemblages

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 2: Insights from Oligocene–Miocene dinoflagellate cyst assemblages

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 1: Insights from late Oligocene astronomically paced contourite sedimentation

Contact Info

Product

Resources

About